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Semin Respir Crit Care Med
DOI: 10.1055/a-2703-4537
Review Article

Cryptogenic Organizing Pneumonia

Authors

  • Michael Z. Root

    1   Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado, United States

  • Joyce S. Lee

    1   Department of Medicine, Division of Pulmonary, Allergy, and Critical Care Medicine, University of Colorado Anschutz Medical Center, Aurora, Colorado, United States
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Abstract

Cryptogenic organizing pneumonia (COP), formerly called bronchiolitis obliterans organizing pneumonia (BOOP), was first described in the 1980s and is classified as a rare idiopathic interstitial pneumonia (IIP). COP classically presents in a subacute fashion following a flu-like illness with fever, non-productive cough, and fatigue. Imaging often reveals diffuse, bilateral, peribronchovascular and peripheral, consolidative and ground-glass opacities although various imaging subtypes also exist. Physical examination may be normal or reveal inspiratory crackles. Hypoxemia, when present, is commonly identified with exertion but can also occur at rest. Diagnostic evaluation relies on excluding secondary causes of organizing pneumonia and includes a thorough history including medications, exposures, and signs or symptoms of underlying rheumatologic disease. Invasive diagnostic testing including tissue sampling allows for histopathologic confirmation of COP while excluding secondary causes including infection and malignancy. Although video-assisted thoracoscopic surgery (VATS) lung biopsy is often the preferred method of obtaining sufficient tissue, less invasive means may be employed based on patient-specific factors. A defining feature of COP is steroid-responsiveness, and most experts recommend prolonged corticosteroid courses (6–12 months). Response to corticosteroids and prognosis are typically excellent. Relapse rates range from 25 to 50% and occur most often during steroid taper or complete withdrawal necessitating additional therapy. Steroid-sparing immunosuppression may be used in select circumstances. Further study is needed to define optimal corticosteroid dose and duration.

Keywords

cryptogenic organizing pneumonia (COP) - organizing pneumonia (OP) - idiopathic interstitial pneumonia (IIP) - bronchiolitis obliterans organizing pneumonia (BOOP) - interstitial lung disease (ILD)


Publication History

Received: 15 August 2025

Accepted: 16 September 2025

Accepted Manuscript online:
18 September 2025

Article published online:
23 October 2025

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